a(n) = Sum_{k=0..n} (-1)^k * binomial(3*n+2*k+1,n-k).
A390544
a(n) = Sum_{k=0..n} (-1)^k * binomial(3*n+2*k+1,n-k).
Terms
- a(0) =1a(1) =3a(2) =13a(3) =67a(4) =378a(5) =2240a(6) =13661a(7) =84850a(8) =533657a(9) =3387166a(10) =21648891a(11) =139131636a(12) =898168945a(13) =5819708026a(14) =37827177191a(15) =246530299923
External references
- oeis: A390544